Nebulisers for production of technical or medical aerosols exist in three main types. The oldest, the so-called jet aerosol apparatus consists of an ejection orifice which gives an expanding flow of air which passes tightly above a tube for the liquid which is to be nebulised. By the pressure reduction in the expanding flow of air the liquid is aspirated in the shape of fine drops from the liquid tube and hits a so-called baffle, where the drips are decomposed into an aerosol, normally characterized by particles from below 1 .mu.m to 10-20 .mu.m, that is an inhomogenous aerosol.
Ultrasound nebulisers are ultrasound waves with high power, which tears part the surface layer in a liquid container. They generate an aerosol with even but relatively large particles, often about 4 .mu.m. However the liquid is heated considerably. So-called "spinning disc" nebulisers use a turbine disc which rotates 20.000 rounds/min. or more. Liquid is supplied at the centre of the disc and forms a thin film which is torn apart at the edge of the disc to a fine aerosol wherein the size can be varied but wherein sub-micronic and homogenous particles can be obtained. The apparatus is not suitable for medical use, expensive and not entirely free of danger.